The subject of the invention is a respiratory assistance device which can be used on patients whose spontaneous respiration is absent or insufficient, whether or not they are placed under artificial respiration.
Various devices are known, such as masks, oral, nasal, endotracheal or tracheotomic catheters or cannulae, designed to form the junction between an artificial and/or anaesthetic respiration apparatus and the respiratory system of a patient. These devices, essentially in the form of tubes, may, according to need, comprise immobilizing means, such as lugs or flanges close to the proximal end, for holding them over the patient""s mouth or nose, or else inflatable cuffs close to the distal end, for holding them by friction in the trachea.
Known devices have significant drawbacks. Thus, for example, when a tube of known type is disconnected from the artificial respirator and the patient needs oxygen-enriched air it is necessary to insert a catheter connected to an oxygen source into said tube. Moreover, in the case of insufficient spontaneous respiration, the patient must necessarily remain connected to the respirator until the complete reestablishment of his spontaneous respiration.
Therefore, in order to overcome these drawbacks, respiratory assistance devices have already been proposed, for example in documents EP-A-0 390 684, EP-A-0 701 834 and EP-A-0 978 291, which devices, apart from the main channel formed by the tube, comprise at least one auxiliary channel, for example made in the wall of said tube, allowing a stream of breathable gas to be injected for the patient""s ventilation, this auxiliary channel emerging in the main channel in front of the distal end thereof.
In these devices, the breathable gas feeding the auxiliary channel is usually pure oxygen. However, some patients, whose body is used to a high level of blood carbon dioxide, are not able to withstand ventilation with pure oxygen, which would lead to a risk of a mild heart attack.
The object of the present invention is to improve the respiratory assistance devices summarized above in order to allow them to take the situation of these latter patients into account.
To this end, according to the invention, the respiratory assistance device comprising a tube which forms a main channel and which is designed to be connected by its distal portion to a respiratory airway of a patient such that said main channel connects the respiratory system of said patient to the outside, said device further comprising at least one auxiliary channel connected to a source of breathable gas in order to be able to blow a stream of such a breathable gas into said respiratory system and emerging in said main channel by at least one distal orifice arranged in front of the distal end of the latter, is noteworthy in that it comprises, between said orifice of said auxiliary channel and said distal end of said main channel, communication means which can be opened and closed and, when open, are capable of forming a passage connecting said main channel to the external environment.
Thus, by virtue of the present invention, when said communication means are open, external air is sucked through them via said breathable gas stream, the air thus introduced diluting said breathable gas that can then be tolerated by the patient whose situation has been summarized above.
Preferably, so that the device can be adapted to all circumstances and to all patients, it is advantageous that said passage connecting said main channel to the environment has a variable cross section. Thus, it is possible to adjust the dilution of the breathable gas by the ambient air in an optimum manner.
In one practical embodiment of said communication means, the latter are of the type with a sideways-drilled rotary ring capable of uncovering passages of different diameters. Such a ring may be mounted directly on said tube or else on a funnel in communication with said main channel.
It is advantageous that, facing the distal orifice of said auxiliary channel, means for deflecting said ventilating breathable gas stream toward the axis of said channel be provided and that said communication means be placed between said deflecting means and said distal end of the main channel. This is because, in this case, said deflecting means create, in said main channel, a vacuum that enhances suction of the ambient air through said communication means.